From secnotif@MICROSOFT.COM Thu Aug 16 00:50:13 2001
From: Microsoft Product Security
To: MICROSOFT_SECURITY@ANNOUNCE.MICROSOFT.COM
Date: Wed, 15 Aug 2001 19:49:56 -0700
Subject: Microsoft Security Bulletin MS01-044
The following is a Security Bulletin from the Microsoft Product Security
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Title: 15 August 2001 Cumulative Patch for IIS
Date: 15 August 2001
Software: IIS 4.0 and 5.0
Impact: Five vulnerabilities resulting in either denial of
service or privilege elevation
Bulletin: MS01-044
Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-044.asp.
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Issue:
======
This patch is a cumulative patch that includes the functionality of
all security patches released to date for IIS 5.0, and all patches
released for IIS 4.0 since Windows NT(r) 4.0 Service Pack 5. A
complete listing of the patches superseded by this patch is provided
below, in the section titled "Additional information about this
patch". Before applying the patch, system administrators should take
note of the caveats discussed in the same section.
In addition to including all previously released security patches,
this patch also includes fixes for five newly discovered security
vulnerabilities affecting IIS 4.0 and 5.0:
- A denial of service vulnerability that could enable an attacker
to cause the IIS 4.0 service to fail, if URL redirection has
been enabled. The "Code Red" worm generates traffic that can in
some cases exploit this vulnerability, with the result that an
IIS 4.0 machine that wasn't susceptible to infection via the
worm could nevertheless have its service disrupted by the worm.
- A denial of service vulnerability that could enable an attacker
to temporarily disrupt service on an IIS 5.0 web server. WebDAV
doesn't correctly handle particular type of very long, invalid
request. Such a request would cause the IIS 5.0 service to fail;
by default, it would automatically restart.
- A denial of service vulnerability involving the way IIS 5.0
interprets content containing a particular type of invalid MIME
header. If an attacker placed content containing such a defect
onto a server and then requested it, the IIS 5.0 service would
be unable to serve any content until a spurious entry was removed
from the File Type table for the site.
- A buffer overrun vulnerability involving the code that performs
server-side include (SSI) directives. An attacker who had the
ability to place content onto a server could include a malformed
SSI directive that, when the content was processed, would result
in code of the attacker's choice running in Local System context.
- A privilege elevation vulnerability that results because of a flaw
in a table that IIS 5.0 consults when determining whether a
process
should in-process or out-of-process. IIS 5.0 contains a table that
lists the system files that should always run in-process. However,
the list provides the files using relative as well as absolute
addressing, with the result that any file whose name matched that
of a file on the list would run in-process.
In addition, this patch eliminates a side effect of the previous IIS
cumulative patch (discussed in the Caveats section of Microsoft
Security Bulletin MS01-026) by restoring proper functioning of
UPN-style logons via FTP and W3SVC.
Mitigating Factors:
====================
URL Redirection denial of service:
- This vulnerability only affects IIS 4.0. IIS 5.0 is not
affected.
- The vulnerability only occurs if URL redirection is enabled.
- The vulnerability does not provide any capability to compromise
data on the server or gain administrative control over it.
WebDAV request denial of service:
- The vulnerability only affects IIS 5.0. IIS 4.0 is not affected.
- The effect of an attack via this vulnerability would be temporary.
The server would automatically resume normal service as soon as
the malformed requests stopped arriving.
- The vulnerability does not provide an attacker with any capability
to carry out WebDAV requests.
- The vulnerability does not provide any capability to compromise
data on the server or gain administrative control over it.
MIME header denial of service:
- The vulnerability only affects IIS 5.0. IIS 4.0 is not affected.
- In order to exploit this vulnerability, the attacker would need
to have the ability to install content on the server. However,
by default, unprivileged users do not have this capability, and
best practices strongly recommend against granting it to untrusted
users.
SSI privilege elevation vulnerability:
- In order to exploit this vulnerability, the attacker would need
to have the ability to install content on the server. However,
by default, unprivileged users do not have this capability, and
best practices strongly recommend against granting it to untrusted
users.
System file listing privilege elevation vulnerability:
- The vulnerability only affects IIS 5.0. IIS 4.0 is not affected.
- In order to exploit this vulnerability, the attacker would need
to have the ability to install content on the server. However,
by default, unprivileged users do not have this capability, and
best practices strongly recommend against granting it to untrusted
users.
Patch Availability:
===================
- A patch is available to fix these vulnerabilities. Please read the
Security Bulletin
http://www.microsoft.com/technet/security/bulletin/ms01-044.asp
for information on obtaining this patch.
Acknowledgment:
===============
- John Waters of Deloitte and Touche for reporting the MIME type
denial of service vulnerability.
- The NSFocus Security Team (http://www.nsfocus.com) for reporting
the SSI privilege elevation vulnerability.
- Oded Horovitz of Entercept(tm) Security Technologies
(http://www.entercept.com) for reporting the system file listing
privilege elevation vulnerability.
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